Part satellite, part drone, part glider: that's perhaps the easiest way to describe the theoretical craft at the center of DARPA's Vulture program, which aims to foster development of an unmanned solar drone capable of flying for up to five years without landing--or replenishment.

Now, with the help of technology from defense contractor Qinetic as well as an $89-million contract from the DoD, Boeing could realize the dream of ultra-sustained flight by 2014, using a 400-foot-wide catamaran-esque design, tentatively called the Solar Eagle. (Pictured above.)

DARPA's basic guidelines for the project are as follows: It wants a heavier-than-air craft (read: not a balloon) capable of hauling a half-ton of equipment with a 5kw energy supply, over a period of five years. For perspective, the longest unmanned flight to date lasted 14 days--the two weeks in the middle of July of this year--and was accomplished by a Qinetic Zephyr drone.

It's an undeniably odd venture, and its advantages over low-orbit satellites or existing reconnaissance drones aren't immediately obvious. To shed a little light on the motivation for this near-$100-million expenditure, here's the closest thing to a project mission statement provided by DARPA:

Vulture technology enables a re-taskable, persistent pseudo-satellite capability in an aircraft package. The technology combines the key benefits of an aircraft (flexibility & responsiveness, sensor resolution, reduced transmit/receive power, affordable deployment) with the benefits of a satellite (on- station persistence, no logistics tail, zero emissions, energy independence, minimal fleet size, absence of in-country footprint). The system has potential in numerous roles: operation as a single platform, as a formation of multiple aircraft or as a constellation providing infrastructure augmentation or recovery.

To translate a bit, the DoD basically hopes to use these drones as cheap, quick-to-launch satellites. Sustained reconnaissance and communications will be their primary duties, and as such, they'll live relatively serene lives, called upon when needed and otherwise left to float peacefully through--or rather, above--the clouds.

Boeing's first test for the craft comes in early 2014, when they're expected to demonstrate a model capable of flying for a month at a time. This is essentially a plausibility test--neither DARPA nor Boeing are certain that current solar and power storage technology is up to the task at hand.